1. Field of the Invention
This invention relates generally to electronic printers wherein multi-page documents to be printed are received as character code signals to be applied to a pattern generator for mapping and rasterization, and more particularly to such printers having means to electronically store the character code signals of a multi-page document and for repeatedly presenting the stored signals to the pattern generator in the proper sequence to produce a plurality of collated printed sets.
2. Description of the Prior Art
Computer work stations, word processors, and the like generally produce print jobs in character code signals, such as for example ASCII code, page description language, page description file formats, and the like. Multi-page document print jobs are queued in a print server, and spooled one page at a time to a pattern generator. The pattern generator converts the coded signals to a rasterized video data stream for printing pixel (picture element) by pixel. When a plurality of collated printed sets of a multi-page document are desired, the print server repeatedly presents the stored character code signals to the pattern generator in the proper page sequence, as often as is needed to produce the desired number of collated printed sets.
During production of a plurality of collated printed sets the character code signals are repeatedly spooled one page at a time from the print server, and the mapping and rasterization process of each page of the multi-page document is repeated for every collated printed set. The mapping process is very processor intensive and, on complex pages, may take as much as a minute per page. In high speed electrostatographic printers, the pattern generator is often unable to keep up with the print engine, which goes into a "skip cycle" mode until the electronic image for the next page to be printed is available. In the skip cycle mode, the print engine continues to run, but without paper feed, and with appropriate adjustment to charging, toning, erasing, and cleaning processes. Reference is made to IBM Technical Disclosure Bulletin Vol. 28, No. 8, January 1986 for a fuller description of the skip cycle process.
There is a predetermined number of skip cycles beyond which it becomes desirable to shut the print process down, either entirely or partially, to save energy as well as wear and tear on the print engine. However, unless the predetermined number of skip cycles are reached, the shutting down and restarting of the print engine can cause more reliability problems than the reduction of the wear and tear would justify.